Expansion of pressure welded passageway panels



P. R. STAPLES Oct. 28,. 1958 EXPANSION OF PRESSURE WELDED PASSAGEWAY PANELS Filed Dec. 1, 1955 FIG. 6

INVENTOR PAUL R. STAPLES ATTORNEY United States Patent EXPANSION OF PRESSURE WELDED PASSAGEWAY PANELS Paul R. Staples, Louisville, Ky., assignor to Reynolds Metals Company, Louisville, Ky., a corporation of Delaware Application December 1, 1955, Serial No. 550,389

4 Claims. (Cl. 29-1573) This invention relates to "pressure welded passageway panels for evaporators and the like.

In expanding the unbonded portions of these panels, there is a marked tendency for the metal, which forms the walls of the expanded passageways, to neck down along the marginal edges of the. passageways, which is to say, closely adjacent the joint between the bonded and unbonded portions of the panels. For example, an expanded wall thickness, which should be of an order of, say 0.030 to 0.032 inch, often necks down as much as .005 to .007 inch so that, in the neck down area, the overall thickness may range from .023. to .027 inch. Consequently, in the absence of proper corrective meas ures, it becomes necessary to increase the thickness of the normal starting sheet metal to a degree sufficient to insure a safe final thickness in the neck down areas. This is objectionable since it necessitates a very substantial increase in the amount of metal contained in a given panel.

The principal objects of the present invention are: substantially to reduce, if not to eliminate, the tendency to neck down; and to strengthen the walls of the passageways throughout their extent and thereby additionally decrease the likelihood of accidental rupture.

All of the more important objects of my invention can be achieved by expanding the panel outwardly against yieldable pressure-loaded dies or platens preferably from a point approximating zero expansion to a point of desired expansion which may be final expansion or slightly in excess of final expansion. In other words, a flat panel is positioned between two dies which preferably engage both faces of the fiat panel from the very beginning to the end of the expansion operation and which are made to resist the expansion in a yieldable manner. I have found that this minimizes and quite often prevents neck down. Furthermore, it effects a working and corresponding strengthening of the passageway-forming metal, along the marginal edges of the passageways where the unbonded portions join the bonded portions of the panel. This does not occur in a case where dies are spaced to require substantial expansion before effective die engagement.

The invention is illustrated in the accompanying drawing wherein:

Figure l is a partly broken plan view of a conventional pressure welded unexpanded passageway panel;

Figure 2 is a section taken along line IIII of Figure 1;

Figure 3 is an enlarged fragmentary sectional detail of a conventionally expanded panel illustrating the neck down condition which is corrected by the present invention;

Figure 4 shows a panel between spring loaded dies which are in the panel receiving position;

Figures 5 and 6 show the panel of Fig. 4 at the beginning and the end respectively of the expansion operation as conducted in the spring loaded dies of Fig. 4;

Figs. 7, 8 and 9 are enlarged fragmentary sectional details of the panel, such as theone expanded in the dies of Figs. 4-6, these views showing how the cross sectional shape of the passageway changes or develops as the expansion operation proceeds; and

Figs. 10 and 11 show a panel at the beginning and the end respectively of the expansion operation when conducted in hydraulically loaded dies.

In carrying out the invention, two foreshortened metal sheets, with a foreshortened stop weld pattern of appropriate design interposed between them, are roll bonded to form a relatively elongate unexpanded panel 1 having unbonded passageway forming portions 2. If this panel be conventionally expanded to form passageways 3, it is very apt to neck down as indicated at 4 in Fig. 3. Con sequently, in the absence of corrective measures which prevent neck down, it becomes necessary to form the panel from metal sheets having a thickness large enough to insure an adequate final thickness in the neck down area. This is objectionable since it necessitates a substantial increase in the amount of metal contained in a given panel over what could be used in the panel in the absence of neck down, and a corresponding increase in the cost of the panel without improving the panel in any In accordance with the presentinvention, neck down is substantially minimized if not eliminated by clamping the panel between yieldable dies or platens and then expanding the panel against the yieldable resistance of the dies. Accordingly the panel 1 is placed between movable dies 5 and 7 which are initially spaced apart a distance sufiicient to receive the panel between them. Thereupon the lower die 5 is hydraulically raised by hydraulic jack 6 until the panel is clamped between the lower die 5 and the upper die 7. Preferably the elevated position to which the lower die is moved, is such that the springs 8 of the upper die are compressed sufficiently to exert a predetermined clamping pressure upon the panel, this clamping pressure being on the order of, say, 200 p. s. i. to 1,000 p. s. i. The hydraulic jack 6 now functions to hold the lower die 5 in that elevated position.

The expansion apparatus 9 is now operated to force hydraulic liquid under pressure into the panel and along the unbonded portions thereof. As the expansion pressure increases the liquid flows throughout the panel and begins to force the upper die 7 upwardly against the yieldable resistance of the springs 8. Where the panel is clamped at the beginning of the operation, with a force of 1,000 p. s. i., it will be necessary to apply the hydraulic liquid at a pressure greater than 1,000 P. S. I. before it will enter the panel and begin to expand the panel.

The maximum pressure used in the expansion operation will depend in a large measure upon the composition of the metal forming the panel. Normally with aluminum panels of conventional composition, a final expansion pressure of 3,000 to 4,000 p. s. i. will be sufficient. Therefore, as the expansion proceeds from minimum to maximum, the expanded passageways will change their contour as indicated in Figs. 7 through 9. Here it will be noted that the fiat crest 11 of the passageways is relatively wide in Fig. 7 but, as the expansion height becomes progressively larger, the crest width becomes progressively smaller as indicated in Figs. 8 and 9. Furthermore, the metal 12, between the crest 11 and the body of the panel 1, will be worked during the expansion and thereby strengthened. Consequently, neck down is not only avoided but the metal, where neck down has heretofore occurred, being worked during expansion, will be much stronger; hence able to withstand higher internal pressures in a safe manner.

The upper die 7 of Figs. 46 is designed to move upwardly until, when the panel is fully expanded, a stop position is reached. If desired, this position. may be determined by designing the springs to exert a clamping force equal to the expansion force when the panel is' fully expanded. Preferably, however, the springs 8 should be somewhat weaker with the dies arranged to move upwardlyagainst the spring'loa'd until they strike the gauge blocks 14 which determine the final position.

The die apparatus shown in Figs. 10 and 11 com prises: an upper stationary die 16; and a lower movable die 17, the latter being supported and moved by a hydraulic jack 18. With this arrangement, the jack is operated to open the dies toreceive the panel and to close the diesto clampthe'panel with aforce not less than thatcreate'd by the" maximumfinal expansion pressure of, say 3,000 p: s. i. Now the expansion fluid is fed to the panelat-a-pressure-of 3;000 p. s. i. Naturally this fluid cannot enterthe panel and expand it unless the clamping pressure is released Accordingly, the lower die 17 ispermittedto-moveslowlydownward, toward and to apositioncorrespondingto full expansion, by releasing theliquid pressure of the hydraulic jack 18 through a suitable valve 19; As the-pressure of the jack 18 decreases, liquid will enter the panel and expand it contemporaneously and correspondingly. When the fully expanded position is reached, the expansion pressure is released and the dies opened to permit removal of theexpanded panel.

Having described my invention, I claim:

1. A method of expanding a pressure welded passageway panel composed of a pair of superposed metal sheets.

containing unbonded potential passageway portions 10- cated between. bonded portions, comprising-z clamping the panel between relatively yieldably-mounted rigid platens having" flush" face-to-face engagement with said unbonded portions; and expanding unbonded portions outwardly against the resistance of said platens to move the platens relatively apart, to flatten unbonded portions engaging said platens, to work the panel metal which extends across the space bet'ween the platens and the bonded portions. ofjthe panel'andto form said unbonded portions into a passageway having substantially the expansion height desired in the final panel.

2. The method" of claim 1. including: expanding the panel against spring loaded platens.

3. The method of claim 1 including: clamping the panel. with. an elevated pressure'of predetermined magnitude.

4. The method' of' claiin 1' including: clamping the panel between fluid actuated platens which are held in position by a fluid at an elevated pressure; feeding an expansion fluid to" the panel at. an elevated pressure; and progressively releasingjth'e platen holding pressure to allowthe expansion fluid to separate the platens and correspondingly expand the panel.

References Cited inithe file of this patent UNITED STATES PATENTS 1,999,229 Benedict Apr. 30,1935 2,259,301 Evans Oct. 14, 1941 2,649,067 Kranenb'erg Aug. 18, 1953 2,662,273 Long Dec. 15, 1953 

